Micro-electronic devices are often manufactured using masks (or reticles) in a lithography process. The latter is one of the principal processes in the manufacture of semiconductor devices, and consists of patterning the electrical circuit's surface in accordance with the circuit design of the semiconductor devices to be produced. Thus, a designed structural element (also referred to as a design structural element) should be converted to the actual structural element by the lithographic process. The lithographic process is highly complex and its parameters can vary from time to time. In addition, a mask that is illuminated in order to imprint the actual structural element is not ideal and can be characterized by variations between ideally identical mask elements.
The performance of micro-electronic devices has always been limited by the variations found in the dimensions of their actual structural elements. Various entities and methods have been used to measure critical dimensions (CDs) of such structural elements.
Recently a more detailed manner to evaluate microscopic structural elements has evolved. It includes obtaining a scanning electron microscope image of an actual structural element, detecting a contour of the actual structural element (referred to as an actual structural element contour) and comparing the actual structural element contour to a contour of a design structural element.
The comparison can be dramatically biased if the actual structural element and the design structural element are not aligned. Manual alignment is time consuming and not very accurate.
There is a need to provide efficient systems and methods for evaluating an actual structural element of an electrical circuit and especially for aligning the actual structural element.